Rolling Dams (Drowning Machines), Revisited

I first learned of the danger posed by the typical dam design found in many Midwest rivers when I researched the Yorkville, IL dam. Here are two videos that better describe that danger.

USACE, Headquarters posted

Low-head dams are found on waterways throughout the U.S. Before you the hit watery trails, review the Low-Head Dam Inventory to see if there’s a dam on your route.

Up, out, and around is always better than going down these dams. If ever in doubt, get out and scout before you continue your journey downstream. 

View more at youtube.com/watch?v=VuO9ZSCtZN4. To locate low-head dams near you and learn more, visit nid.sec.usace.army.mil.

Tim Williams: They could fix all of these by making the middle an inch or 2 lower. It creates a strong, central current that doesn’t vortex, and pulls debris out of the horizontal vortex to deposit it downstream.

To be clear, this makes them safer, but still not safe.

Tim Williams: I built models and tested them in the water flow tanks at Central State University, back in 2008. There are other solutions that also create a strong central water stream that breaks the vortex. Adding an upstream semicircular section to replace a section in the middle of the dam works to increasing edge length for more flow per width of dam without changing the height of the dam.

A four minute video that demonstrates the danger.


A 24 minutes video that explains the "hydraulic jump" that causes the rolling current that causes the drownings. It is the backwards rolling current generated near the face of the dam that causes these dams to be called "rolling dams." Another thing I learned is that all of the air trapped in the recirculating current makes it foamy and even harder to swim in.






When I first saw the above video many moons ago, I also found a video that trains first responders how to do a safe rescue. Unfortunately, I now can't find that video. If I remember correctly, the jest of the video was to first string a rope from one bank to the other.

(new window) Even a relatively big outboard motor is of no use.   I'm glad someone cropped this profile video into the following horizontal format.


An unflippable whitwater raft has been developed that allows rescue workers to approach the face of a dam.

Screenshot @ -0:21

(new window)   I learned of this video because he asked for permission to use one of my videos. Since it is licensed CC BY, he didn't need permssion. But I was glad to learn about the video. I see at 4:55 that this is the video that used it.

Satellite
Cornelia Reade-Hale shared:
Removal of Kentucky dam where multiple people have drowned set to begin Tuesday [June 8,2021]
"Multiple people have drowned at the dam, most recently in October 2018 when 35-year-old kayaker Matthew Hughes, of Lexington, got sucked into the undertow after holding onto a rope for nearly two minutes."

0:49 video of "SLATERSVILLE Reservoir.  December 18, 2023."
[A fixed weir dam creating a big hydraulic jump and backflow towards the dam.]

USACE, Pittsburgh District posted

🚨 We need to have a talk.

About fixed-crest dams.

If you’ve never heard of them, a fixed-crest dam is a structure that stretches all the way across a river or stream, usually with just a small drop — anywhere from 1 to 15 feet. Seems harmless, right?

Wrong. These things are extremely dangerous.

They’re known in the paddling world as “drowning machines” because of the powerful, circulating current they create. Once you go over, the water can pull you back in and trap you — even if you're wearing a life jacket. Even strong swimmers can’t escape the force. Tragically, many victims have been would-be rescuers who didn’t make it back either.

The scariest part? You often don’t see these dams from upstream until it’s too late. They form an infinity pool visual effect, but not the kind you’d enjoy on top of a luxury hotel in Dubai. 

Here’s how to stay safe out there:

🗺️ Check a map ahead of time and ask locals about dam locations

👀 Stay alert on the water

🚫 Never try to paddle over — always turn around well before the dam

📢 Obey warning signs and barriers

📍 Let someone know your plans before heading out

📞 If someone’s in trouble, don’t jump in — call 911 and use a rope or throw bag to help

[Highland Park dam and bridge.]

This video scares me just to watch it. That water was up to his knees and flowing pretty fast. And there is a foamy hydraulic jump of at least a foot or so at the base of the dam.

The Kankakee, IL and Wilmington, IL Dams each have Class C hydraulic jump (submerged and rolling).

Carpentersville, IL Dam seems to be designed to create a Class A (stretched out and safe) hydraulic jump. But I still would not want to try going over that dam!

Hofmann Dam in Riverside, IL, is an example where an obsolete mill dam has been removed.

The Montgomery, IL Dam also appears to have a safer design.

This video should get you started on other videos of dam removals.

Of the 13 dams that used to be on the Fox River in Illinois, two of them have already been removed. There are plans to remove the Carpentersville, IL Dam, even though it has one of the safer designs.